The formation of calcium salt scales such as calcium phosphate, calcium oxalate, calcium carbonate, and calcium silicate, during liquid food processing is a significant problem for the food and beverage industry, particularly for breweries, vegetable juice processors, and evaporators in food processing plants. Exemplary liquid food streams that require processing include, but are not limited to: milk, whey, whey permeate, fruit and vegetable juices, calcium fortified beverages, sugar, corn wet milling steeping liquor, and fuel ethanol process streams from corn, sugar, or other biomass conversions. In particular, calcium phosphate may form during the processing of milk, and calcium oxalate may form during the processing of sugar, spinach, and other juices.
The formation of the calcium salt scales on the surface of the processing equipment causes scaling or fouling of the system, decreasing the flow rate and the run-time of the process. Various stages of food processing operations involve concentrating liquid food process streams, such as during evaporation, filtration, or pasteurization. Typically, scaling of the equipment occurs during heat exchange stages, such as the evaporation stage and the ultra high temperature (UHT) stage of food processing operations. The heat facilitates the formation and deposition of calcium salts on the surfaces of the equipment, decreasing the flow rate and run time of the equipment. For example, during the UHT stage, the liquids are pasteurized at temperatures of around about 146 degrees Celsius as the liquid goes through the tube.
Current methods for removing the calcium salts deposited on the surface of the equipment typically involve using the alkaline salt of ethylene diamine triacetic acid (EDTA), a biodegradable chelant, or strong solutions of nitric acid, phosphoric acid, or sulfuric acid. In the case of calcium oxalate, hydrochloric acid and hydrofluoric acid may be used. The solutions are used to dissolve the calcium salts in order to remove the scaling from the surface of the equipment. The equipment is cleaned daily with the calcium salts being removed during an acid rinse cycle.